Biaxially blow-molded bottle-shaped container having pressure responsive walls

ABSTRACT

A biaxially blow-molded bottle-shaped container (1) of synthetic resin includes a generally square cross-sectional body portion (2). A panel wall (3) for absorbing a reduced pressure generated in the bottle-shaped container is provided on a flat wall portion at each side of the body portion. Depressed cross grooves (5) are provided spaced apart in parallel in a ridge line portion between the adjacent panel walls (3, 3). The body portion may be cut-off at corners thereof to provide vertically elongated flat surfaces (4), and depressed cross grooves (5) may be provided spaced apart in parallel in each flat surface (4).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a biaxially blow-molded bottle-shapedcontainer made of synthetic resin, more particularly to a constructionof a body portion of a biaxially blow-molded bottle-shaped containermade of polyethylene terephthalate resin.

2. Prior Art

There has hitherto been widely used a bottle-shaped container which isproduced by biaxially blow-molding a preformed parison of syntheticresin such as polyethylene terephthalate resin. Such a bottle-shapedcontainer has an excellent resistance to contents which is provided bysufficiently orienting the preformed parison. The bottle-shapedcontainer is formed with a thin wall and is light. The container has anexcellent shock resistance and can be inexpensively produced by massproduction.

However, there is a problem that when the bottle-shaped container isfilled with a hot liquid content and subsequently cooled, the wall ofthe body portion of the bottle-shaped container is deformed owing to areduced pressure in the container.

Accordingly, there has been known to provide panel walls in the bodyportion to absorb the reduced pressure by an elastic deformation of thepanel walls. It is required that each panel wall is relatively largeflat wall construction due to the following reasons. (1) By the reducedpressure, the panel wall is more deformable than the rest of the bodyportion. (2) The depression deformation occurring on the panel wall isan elastic deformation. (3) Only a little depression-deformationdecreases the volume of the container a large amount.

A large biaxially blow-molded bottle-shaped container having acylindrical body portion of a circular section can be provided withreduced-pressure absorbing panels only by forming vertically extendedflat portions on the peripheral surface portion of the body portion.Therefore, the shape of the panel walls on the body portion of thecontainer is vertically elongated and as a result, the panel walls ofthe container cannot be greatly deformed. Therefore, the volume of thebottle-shaped container does not greatly vary by thedepression-deformation of the panel walls on the body portion of thebottle-shaped container.

A large biaxially blow-molded bottle-shaped container having acylindrical body of a square section can be provided withreduced-pressure absorbing panels by forming a flat portion on each sideof the square cylindrical body portion. Each flat portion can be easilyand sufficiently deformed and has a large flat area so that the volumeof the container can be greatly varied by the deformation of the flatportions. Thus, each flat portion effectively acts as a panel wall forabsorbing the reduced pressure.

FIG. 3 illustrates a conventional bottle-shaped container 1' having asquare cylindrical body portion 2'. Each side surface of the bodyportion 2' continues to adjacent both side surfaces through ridge lineportions, respectively. Each side surface of the body portion isprovided with a reduced-pressure absorbing panel wall 3' for absorbingthe deformation of the wall of the bottle-shaped container caused by thereduction of the pressure in the container.

When the pressure in the bottle-shaped container 1' is reduced, thepanel wall 3' is deformed and inwardly bent to cause an internal stressextended to the ridge line portions. The ridge portions are pillarportions for maintaining the shape of the bottle-shaped container andmust have a high mechanical strength. If the ridge portions are deformedby the internal stress, the mode of bending of the panel wall 3' is notconstant and the body portion of the square cylindrical shape isdeformed. In particular, large bottle-shaped containers are greatlydeformed by the reduced pressure, because the large bottle-shapedcontainers have a thin wall owing to a deep orientation and a largeheight thereof. Thus, the large bottle-shaped containers are required tohave ridge line portions having a high mechanical strength.

In order to eliminate the aforementioned problems, there has beendesigned to provide elongated grooves 5' in the ridge line portions.Such an elongated groove 5' acts as a reinforcing rib to increase themechanical strength in the ridge line portion to thereby prevent theridge line portion from undue strain deforming owing to the deformationof the panel wall 3'.

Generally, biaxially blow-molded bottle-shaped containers produced in afactory are packed in cases made of a corrugated cardboard andtransported to other factories for filling liquid into the bottle-shapedcontainers. The bottle-shaped container is light, but is bulky.Consequently, in order to efficiently transport the bottle-shapedcontainers, it is desirable that a number of bottle-shaped containersare closely packed in each cardboard case.

However, when uncapped bottle-shaped containers as shown in FIG. 3 areclosely packed within the cardboard case and are subjected to anexternal pressing force over a limit of the resistance force of theridge line portions having a mechanical strength sustained by theelongated grooves 5', the ridge line portions are inwardly bent toresult in a bending deformation. This bending-deformation issemi-permanently since the elongated grooves 5' act as reinforcing ribsin the condition of bending deformation to prevent the ridge lineportions from elastically returning back to the original form.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the aforementionedproblems and disadvantages in the prior art and to provide abottle-shaped container adapted for preventing the ridge line portionsfrom inwardly bending and semi-permanently deforming by the externalpressing force applied to the body portion of the bottle-shapedcontainer, and also maintaining necessary mechanical strength.

According to the present invention, there is provided a biaxiallyblow-molded bottle-shaped container (1) of synthetic resin including agenerally square cross-sectional body portion (2), wherein a panel wall(3) for absorbing a reduced pressure generated in the bottle-shapedcontainer is provided on a flat wall portion at each side of the bodyportion, and depressed cross grooves (5) are provided spaced apart inparallel by a constant distance in a ridge line portion between theadjacent panel walls (3, 3).

The body portion may be cut-off at corners thereof to provide verticallyelongated flat surfaces (4), and depressed cross grooves (5) may beprovided spaced apart in parallel by a constant distance in each flatsurface (4).

When a pressure in the bottle-shaped container is reduced by coolingafter a hot liquid is filled in the container, the reduction of thepressure is sufficiently absorbed by elastic depression-deformation ofthe panel walls (3) of the body portion. When the panel walls (3) areelastically depression-deformed to cause an internal stress, thisinternal stress acts to the ridge line portions between adjacent panelwalls (3, 3'). The internal stress consists of a component of forcewithdrawing inwardly the ridge line portions and a component of forcepressing each ridge line portion from the opposite sides thereof.

The cross grooves (5, 5) depressed in the ridge line portion will act toinwardly bend the ridge line portion against the force withdrawinginwardly the ridge line portion. The ridge line portion is subjected tothe withdrawing force as well as the pressing forces from the oppositesides thereof as mentioned above. The ridge line portion tends toprotrude radially and outwardly owing to the forces pressing the ridgeline portion from the opposite sides thereof. Thus, the ridge lineportions act as reinforcing ribs against the withdrawing force andprovide a high mechanical strength.

Accordingly, when uncapped bottle-shaped containers (1) closely packedwithin the cardboard case are subjected to a force pressing sidewardlythe body portion (2) and the pressing force increases higher than apredetermined value, the ridge line portions are elastically deformedinwardly all over the same owing to the cross grooves which aretransversely depressed in the ridge line portion. Thus, the externalpressing force is absorbed by the elastic bending-deformation of theridge line portion all over the same. In this case, since thedeformation of the ridge line portions is an elastic deformation, thedeformed ridge line portions are elastically returned to the originalform when the external pressing force is released. Accordingly the ridgeline portions are not semi-permanently deformed.

A corner of the body portion (2) may be cut-off to provide flat ridgeline portions. Thus, each ridge line portion has corners (7) formed atits opposite sides and each cross groove (5) also has corners (7a)formed at its opposite sides. These corners (7 and 7a) arranged at theopposite sides of the each ridge line portion can act as reinforcingribs against an elastic bent deformation of the central portion of theridge line portion. Thus, the opposite side portions of the ridge lineportion have a stress to extrude radially and outwardly from the ridgeline portion by a force pressing the ridge portion from the oppositesides thereof due to the deformation of the panel wall. As a result, thefunction mechanically supporting the ridge line portion in thedeformation of the panel wall is increased. Since the central portion ofthe ridge line portion is flat, the ridge line portion can beelastically deformed by the external pressing force. Consequently, whenthe body portion of the bottle-shaped container which is not filled withliquid is subjected to a large external pressing force, the whole ridgeline portion can be more greatly elastically deformed withoutsemi-permanent bending-deformation and as a result the faculty ofabsorbing the external force is increased by the elastic deformation ofthe whole ridge line portions and also a sufficient mechanical strengthto maintain the shape of the bottle-shaped container is sustained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an embodiment of a biaxially blow-moldedbottle-shaped container according to the present invention;

FIG. 2 is an enlarged sectional view of the essential portion of thebottle-shaped container shown in FIG. 1; and

FIG. 3 is a front view of a conventional biaxially blow-moldedbottle-shaped container of prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention will hereinafter bedescribed with reference to the drawings.

A bottle-shaped container 1 is a large bottle having a thin wall whichis produced by biaxially blow-molding a preformed parison made of asynthetic resin. In this embodiment, the bottle-shaped container 1 ismade of a polyethylene terephthalate resin.

The bottle-shaped container 1 has a generally square cross-sectionalbody portion 2. This body portion 2 is provided at each side of thecontainer in about the two-third part of the lower portion thereof withpanel walls 3 for absorbing deformation caused by reduced pressure inthe container.

Each panel wall 3 may be provided at its central portion with one ormore depressed portions 3a which absorb the reduced pressure in thecontainer. The depressed portion 3a effectively permits deformation ofthe whole panel wall 3 owing to the reduced pressure without unduestraining. In the illustrated embodiment, two depressed portions 3a, 3aare formed at positions vertically spaced apart in each panel wall oneach side of the body portion, but an elongated depressed portion may beprovided in each panel wall 3.

Referring to FIGS. 1 and 2, a ridge line portion at each corner of thegenerally square cross-sectional body portion 2 may be cut off toprovide an elongated flat surface 4 which is vertically extended at eachcorner. Corner portions 7 are formed at the opposite sides of the flatsurface 4. The flat surface 4 is provided with a plurality of depressedcross grooves 5 spaced apart in parallel. A cross ridge 6 is formedbetween adjacent cross grooves 5, 5 as a portion of the flat surface 4.The cross groove 5 is extended in the circumferential direction of thebody portion over the width of the flat surface 4. The cross groove 5has corners 7a formed therein. These corners 7a correspond to thecorners 7, respectively. Vertical ribs 5a are formed between theopposite ends of the cross grooves and the corners 7a, respectively. Theupper and lower ends of each cross groove 5 act as cross ribs 5b.

The corners 7 and 7a continuously form a vertical rib which resists toan internal stress in the ridge line portion when the panel wall 3absorbs the reduced pressure generated within the bottle-shapedcontainer 1. The vertical ribs 5a and cross ribs 5b together with thecross ridge 6 absorb the external pressing force applied to thebottle-shaped container 1 to elastically deform the flat surface 4.

The bottle-shaped container having the aforementioned constructionaccording to the present invention can carry out the following effects.

Since each ridge line portion stably and rigidly supports the panel wallwhich is elastically depression deformed owing to the reduced pressureto resist the internal stress caused by the depression-deformation ofthe panel wall, each panel wall for absorbing the reduced pressure inthe bottle-shaped container is elastically depression-deformed.Accordingly, the configuration of the bottle-shaped container can bemaintained in the better form when deforming due to the reduced pressuregenerated within the bottle-shaped container.

When the body portion of the bottle-shaped container which is not filledwith a content is subjected to a high external pressing force in thelateral direction, the whole ridge line portions are greatly elasticallydeformed so that the external pressing force can be absorbed by theelastic deformation of the ridge line portions. Thus, the ridge lineportions are not permanently deformed in the form of a buckling- orbending-deformation by the external pressing force to completely preventoccurring of a bottle-shaped container of inferior quality owing to thepermanent buckling-deformation of the ridge line portions.

Since the ridge line portions in the corners of the square cylindricalbody portion are provided with depressed cross grooves, fingers aresnugly fitted in the cross grooves when the body portion is gripped byone hand. Therefore, such a large bottle-shaped container can be safelyhandled by one hand.

Since the cross grooves are simply depressed in the ridge line portions,the construction is simple and can be easily molded by the conventionalmanner without necessity of any particular molding technique.

What is claimed is:
 1. A biaxially blow-molded bottle-shaped containerof synthetic resin, comprising a generally square cross-sectional bodyportion having four sides and ridge line portions between each pair ofadjacent said sides,each said side having a flat wall portion which as apanel wall including means for absorbing a reduced pressure generated inthe bottle-shaped container, and at least one of said ridge lineportions having depressed cross grooves spaced apart in parallel.
 2. Abiaxially blow-molded bottle-shaped container of synthetic resin,comprising a generally square cross-sectional body portion having foursides and four vertically elongated flat surfaces, each said flatsurface being positioned between a pair of adjacent said sides,at leastone of said flat surfaces having depressed cross groves spaced apart inparallel and each said side having a flat wall portion which has a panelwall including means for absorbing reduced pressure generated in thebottle-shaped container.